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Refractive Errors

What is normal vision?

In order to better understand how certain problems can affect your child's vision, it is important to understand how normal vision occurs. For children with normal vision, the following sequence takes place:

Illustration demonstrating normal vision

  1. Light enters the eye through the cornea, the clear, dome-shaped surface that covers the front of the eye.
  2. From the cornea, the light passes through the pupil. The amount of light passing through is regulated by the iris, or the colored part of your eye.
  3. From there, the light then hits the lens, the transparent structure inside the eye that focuses light rays onto the retina.
  4. Next, it passes through the vitreous humor, the clear, jelly-like substance that fills the center of the eye and helps to keep the eye round in shape.
  5. Finally, it reaches the retina, the light-sensitive nerve layer that lines the back of the eye, where the image appears inverted.
  6. The optic nerve carries signals of light, dark, and colors to the area of the brain (the visual cortex), which assembles the signals into images (our vision).

What are refractive errors?

The following are the most common refractive errors, all of which affect vision and may require corrective lenses for correction or improvement:

Illustration demonstrating astigmatism

Illustration demonstrating hyperopia

Illustration demonstrating hyperopia corrected

What causes refractive errors?

Refractive errors (myopia and hyperopia) have been found to cluster in families. A variety of inheritance patterns have been observed including dominant (one gene passed from a parent with a refractive error to a child), recessive (caused by two genes, one inherited from each parent who may/may not have a refractive error), and multifactorial (combination of genes and environment). Refractive errors are present in a number of genetic disorders, such as Marfan syndrome and Down syndrome.

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